Have the Google+ profile image URLs returned by the Google APIs changed?

Question

So, I use the Google API to get the profile of the people profile using my user_id. The Google API returns JSON, for example:

{
    image: {
        url: "https://lh5.googleusercontent.com/OGjgCn9fCPk/AAAAAAAAAAI/AAAAAAAAASU/AitRTc5cUyg/photo.jpg?sz=50",
        isDefault: false
    }
}

My question is: is this URL changing? I mean, will it change if the user changes the image of his profile or some kind of CDN restructuring occurs.

Do I need to extract it every time? Or can I just save and use it forever?

If this is not some period of time for which I can save, use it directly and update after this time?

UPDATE:

So, if we change the profile picture, the URL will change. Both the old URL and the new URL point to the same new profile picture.

- - , Google URL-? ( ) ?